Program: PBCORR Purpose: Corrects maps for primary beam correction Category: MANIPULATION File: pbcorr.shl Author: M. Vogelaar Keywords: INSET= Input set (and subsets). Maximum number of subsets is 2048. BOX= Frame for input subsets. [entire subset] OUTSET= Output set and subset(s) for the result. The number of output subsets is the same as the number of input subsets. POS= Coordinates for which user wants [stop] to know the primary beam correction. This keyword is asked only if MANUAL=Y is specified. Maximum number of coordinate pairs is 64. *** BACK= If user selects 'N' (default), a primary [N] beam correction is applied. If 'Y' is selected, an attenuation is applied to your maps. *** MANUAL= If user wants to apply correction [N] (or attenuation) on single points, select 'Y'. End the session by pressing . *** OPTION= Give cutoff behaviour: 1/2/3/[4] For the manual mode only option 1 applies. The option cannot be changed in that case. FREQUENCY= Give frequency: [1.415 GHZ] If PBCORR cannot find a proper frequency, the frequency is asked with FREQUENCY= The keyword accepts a number and a unit. If no unit is given, the number is in Ghz. Otherwise, a conversion is done to Ghz. The possible units to convert from are for example MHz, Hz, but also cm (all upper- or lowercase). The keyword is asked unhidden only once. Description: PBCORR corrects an image for the primary beam effects of WSRT, VLA (VLAP), ATCA (Australia Telescope Compact Array) FST antennas and the millimeter arrays IRAM-PdB, NMA (Nobeyama), OVRO and BIMA. The correction is proportional to the square of the distance from the pointing position. The coordinates of the pointing position are taken from the header (items PCRA and PCDEC, values in degrees). If these descriptors cannot be found, the physical values of (pixel) position (0,0) is substituted and the user is warned. There is a cutoff in the distance: Outside the validity range, the correction is set to a value depending on OPTION= For WSRT and VLA The cutoff occurs at a primary beam sensitivity of 2.3% of the value at the beam center, i.e. where the Antenna Power Spectrum is equal to 2.3/100. For the Fleurs telescope the cutoff is (at 21 cm) at a distance of 2.8 degrees. For the ATCA the cutoff occurs for RF = 50 arcmin GHz in all bands. Possible values for OPTION= OPTION=1 : Return 0 if beyond cutoff, i.e. do not correct image values beyond cutoff. OPTION=2 : Return min. allowed correction beyond cutoff. The function calculates this value for different telescopes. OPTION=3 : Disable cutoff, i.e. return values that correspond to coordinates outside the validity range of the correction function. OPTION=4 : Return blank if beyond cutoff. Notes: The correction formulas are described in pribeam.dc1 Updates: Mar 2, 1990: MV, Document created. Apr 8, 1992: MV, OPTION= included. Jul 24, 1992: MV, Document changed for new pribeam routine. Jun 9, 1993: MV, Document changed for new pribeam routine. (Millimeter arrays, Australia Telescope)